Acoustical and fire resistant particleboard

ABSTRACT

A high-density particleboard of great sound attenuation and resistance to heat and flame, comprising wood particles, a suitable binder, and a compound having a density of at least 4.

United States Patent Inventor Andrew E. Carmellini Brookfield, Conn.App]. No. 69,145 Filed Sept. 2, 1970 Patented Dec. 28, 1971 Assignee U.S. Plywood-Champion Papers Inc.

New York, N.Y.

ACOUSTICAL AND FIRE RESISTANT PARTICLEBOARD 9 Claims, No Drawings U.S.Cl 161/168, 161/165, 161/166, 161/403 Int. Cl B32b 5/14, B32b 5/16, B32b21/02 Field 01 Search 161/ l 65, 166, 168, 403

Primary Examiner-William J. Van Balen Attorneys-James M. l-leilman andHeilman & Heilman ABSTRACT: A high-density particleboard of great soundattenuation and resistance to heat and flame, comprising wood particles,:1 suitable binder, and a compound having a density of at least 4.

ACOUSTICAL AND FIRE RESISTANT PARTICLEBOARD A high-density particleboardof great sound attenuation and resistance to heat and flame, comprisingwood particles, a suitable binder, and a compound having a density of atleast 4.

The present invention is concerned with a high-density particle boardwhich has excellent acoustic properties with respect to soundattenuation and which is also highly resistant to flame and heat. Theparticleboard comprises wood particles, a suitable binder and particlesof a dense compound, having a density of at least 4, for example andpreferably a barium compound, such as barium sulfate.

In the building and construction industry it is very desirable to have aboard, panel, or door which is characterized by having a high fire andflame resistance, and which also has excellent sound attenuation. Thusmany types of construction have been suggested to attain thesecharacteristics without impairing other qualities such as strength,wearability and pleasing appearance.

Thus the present invention is concerned with a particular type ofstructural element namely a particleboard structure which is processedand manufactured in a manner to impregnate or fill the intersticesbetween the particles or wood chips with particles of a dense fireproofcompound. The fireproofing compound will also function to greatlyimprove the acoustical properties by significantly reducing the soundtransmission coefficient.

The term particleboar is intended to cover any board comprisingparticles of wood bonded together. The bonding is usually accomplishedby the application of heat and pressure in conjunction with natural orsynthetic resins or other bonding agent. The wood particles may be inthe form of chips, granules, slivers, shavings, flakes and the like.

Suitable bonding agents are, for example, phenolformaldehyde resins,ureaformaldehyde resins, resorcinol, various glues and the like. Thesebonding agents may be used in any concentration such as about 3 to about40 percent by weight based on the weight of thedry wood particles.

A particularly desirable particleboard structural element is one inwhich a core layer comprises randomly arranged wood particles whereinunder usual manufacturing conditions air spaces exist between particles.In accordance with the present invention these air spaces or voids arefilled with a high-density substance. If desired the face layers tothecore comprise a relatively thin layer of superimposed unoriented fiatwood shavings arranged substantially parallel to the outerfaces of thefinished board. The air spaces or voids between these relatively flatshavings are also filled with particles of the'dense substance.

One type of the above nonhomogeneous particle board is Novoply"(trademark of U.S. Plywood Champion Papers Inc.) which is manufacturedunder US. Pats. Nos. 2,642,371 and 2,686,143. Obviously, the inventionis equally applicable to homogeneous boards of relatively large andthick core particles or relatively thin flake boards.

In one embodiment of the present invention the individual wood particlesof which the core material consists have a length of about to 50 mm., awidth of about 5 to l0 mm., and a thickness not exceeding several mm.preferably about 1 to 3 Sufficient materials are used in the core tosecure a core thickness to slightly less than about inch, inch or H4inches and 1% inches. When the face plies are applied thereto thefinished product will have the standard commercial thickness of about $6inch, 56 inch or PA inch and 1% inch (the latter sizes for cores fordoors to which expensive veneers or high-pressure laminates are bonded).

The binder substance in the core layer of the present invention mayamount to a very small percentage, e.g., to about 3.5 to 4 percent byweight of the weight of the wood particles, while the binder substancein the outer or face layers may amount to about 10 to 14 percent byweight of the weight of the wood shavings. It should be noted thatpreferably the percentage of binder substance in the outer layers issubstantially larger than the percentage of the binder substance in thecore layer.

The flat wood shavings comprising the face plies are relatively large insurface area such as lengths from about Va inch to llz inches and widthsfrom about 54 inch to inches. They are however relatively thin and havea thickness of about 0.5 mm. to 2.0 mm. such as about l.0 mm.

In the preferred embodiment of the present invention the number of thesuperimposed shavings is at least 2 and not more than 5 at any part ofany of the outer layers. These outer layers or plies are relatively thinand have a thickness of about I to 3 mm. such as about l.5 mm. The corelayer is substantially thicker than any of the outer or face layers andhas a thickness equal to many times the thickness of each of the outeror face layers. Hence the core thickness may vary from nearly )6 inch toover 1% inches. 1

The high-density particleboard of the present invention is utilized toproduce structural units having high-acoustical attenuation or whichproduces a very high-sound transmission loss. The particleboard of thepresent invention is obtained by utilizing particles of a solid materialas an inorganic filler. The preferred solid material comprises a bariumsalt, and particularly barium sulfate which has an overall specificgravity of about 4.5. The solid material particles such as the preferredbarium sulfate are homogeneously dispersed among the wood particles.

Barium sulfate is particularly important because of its availability andcheapness. For example, it is believed that the cost of lead ranges from15 to 18 cents per pound while bariurn sulfate ranges from 1 to 2 centsper pound. Barium sulfate is greatly preferred, but other densematerials may be used providing they possess a specific gravitypreferably above 4.0 or at the minimum, above 3.0.

Compounds of elements which fall into this category possess one or moreof the following anionic moieties, the sulfide,

the oxide, the carbide, the iodide, the boride, the selenide, the

chloride, the silicide, the telluride, the carbonate, and/or thesulfate. One or more of the above-mentioned anionic groups of thefollowing elements (listed below), possess a density of 4 or more:

vanadium eropium tantalum gallium tellurium indium thorium iron tin leadtungsten magnesium zinc manganese zirconium molybdenum aluminumneodymium antimony nickel arsenic niobium barium osmium bismuthpalladium calcium platinum cadmium rhodium cerium silver chromium sodiumcopper strontium Of the foregoing, preferred substances are leadsulfide, lead iodide, thoriumboride, lead carbonate, iron sulfide andstrontium carbonate. Other excellent substances are iron carbonate andiron boride.

While relatively large particles of heavy solid filler may be embeddedthroughout the mass of the wood particles, for example, heavy particleswhich pass through about 100 mesh screen, it is preferred that the heavyparticles utilized be relatively fine. For example, a mass of particleswherein at least percent pass through a 250 mesh screen aresatisfactory, but a mass of heavy particles wherein at least 90 percentpass through a 325 mesh screen produces better results. When relativelyfine particles are used a very high-quality acoustical panel is secured.This solid heavy material which is added to the binder, as mentionedabove, should have a specific gravity between 3.0 to 4.0 and preferablyabout 4.5.

The quantity of heavy substance particles used may vary widely, as forexample from about 10 to 150 percent by weight based on the weight ofthe wood particles. A preferred amount is about 100 percent based on theweight of the wood particles present.

A very desirable board of the present invention is one wherein 75 to 125percent such as about 100 percent by weight of heavy particles are usedbased on the wood particles in the core, and wherein the size of theheavy particles are such that at least 90 percent pass through a 250mesh screen. The same amounts of heavy particles may be used in the faceplies except that 90 percent of the face ply heavy particles passthrough a 325 mesh screen as stated above.

A very desirable panel is secured if the amount of heavy particles usedin the face plies is about 25 percent to 50 percent by weight based onthe wood particles in the face plies. Thus while both the core and faceplies contain heavy particles, having different sizes of particles anddifferent amounts in the core as compared to the face plies, a sharpinterface will be secured between the core and face plies which willfunction to further attenuate sound transmission.

The panels are prepared by mixing the wood particles, the bonding agentand the heavy particles as desired. The panels are then cured at atemperature in the range from about 150 F. preferably 275 to 330 F. suchas 300 F. for a time period in the range from about 5 minutes to 1 hourssuch as about minutes. The pressure is in the range from about 100 to2,000 lbs. per square inch, preferably in the range of about 400 to1,000 lbs. such as about 800 lbs. per square unit.

In order to further illustrate the present invention the followingexample is given.

EXAMPLE A number of /4X4' 8' panels were prepared using relatively smallwood chips as a core and wood flakes as the surface plies. These panelswere prepared by mixing the bonding agent, the wood particles and thebarium sulfate, and then cured at 345 F. and at a pressure of 800 p.s.i.for one hour.

These panels contained the following amounts of barium sulfateparticles:

Panel A. l6% by weight 8. 73% by weight C. l00% by weight The densitiesof these panels were in the range of 0.95 to L00 as compared to 0.67 fora panel containing no barium sulfate.

Upon testing the STC rating of a conventional panel was 22db. whereasthe STC rating of Panel C was 34 to 35db. as compared to a gypsum wallof 32.

Also the panels were excellent in that fallout of barium salt form thesurfaces was nonexistent. The salt behaved like hardened cement afterpressing.

The embodiment of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A sound attenuating, fire resistant panel comprising wood particlesbound together by a bonding agent and characterized by having heavyparticles of a density of at least 3 between said wood particles.

2. Panel as defined by claim 1 wherein said particles consistessentially of barium sulfate.

3. Panel as defined by claim 1 wherein said panel is characterized by acore layer of randomly arranged wood particles and face plies ofrelatively flat superimposed wood shavings.

4. Panel as defined by claim 3 wherein the amount of heavy particlespresent is in the range from about 75 to I25 percent by weight based onthe weight of the wood particles.

5. Panel as defined by claim 4 wherein the heavy particles present inthe core are of such a size that at least percent pass through a 250mesh screen and the heavy particles present in the face plies are ofsuch a size that at least 90 percent gas through a 325 mesh screen.

6. anel as defined by claim 5 wherein the amount of bonding reagent usedin the core is about 3.5 to 4 percent by weight based on the woodparticles and wherein the amount of bonding agent used in the face pliesis about 10 to 14 percent by weight based on the wood particles.

7. Panel as defined by claim 6 wherein the thickness of the core is inthe range from about A inch to 1% inches and the thickness of the faceplies is in the range from about 0.5 to 2.0

8. Panel as defined by claim 1 wherein said wood particles and saidheavy particles are bonded together by curing said bonding agent at atemperature in the range from about 400 to 1,000 p.s.i. for a timeperiod of about 5 to 30 minutes.

9. Panel as defined by claim 5 wherein the amount of heavy particlesused in the core is about 75 to percent by weight based on the wood coreparticles and the amount of heavy particles used in the face plies isabout 25 to 50 percent by weight based on the weight of the wood faceply particles.

2. Panel as defined by claim 1 wherein said particles consistessentially of barium sulfate.
 3. Panel as defined by claim 1 whereinsaid panel is characterized by a core layer of randomly arranged woodparticles and face plies of relatively flat superimposed wood shavings.4. Panel as defined by claim 3 wherein the amount of heavy particlespresent is in the range from about 75 to 125 percent by weight based onthe weight of the wood particles.
 5. Panel as defined by claim 4 whereinthe heavy particles present in the core are of such a size that at least90 percent pass through a 250 mesh screen and the heavy particlespresent in the face plies are of such a size that at least 90 percentpass through a 325 mesh screen.
 6. Panel as defined by claim 5 whereinthe amount of bonding reagent used in the core is about 3.5 to 4 percentby weight based on the wood particles and wherein the amount of bondingagent used in the face plies is about 10 to 14 percent by weight basedon the wood particles.
 7. Panel as defined by claim 6 wherein thethickness of the core is in the range from about 1/4 inch to 1 1/4inches and the thickness of the face plies is in the range from about0.5 to 2.0 mm.
 8. Panel as defined by claim 1 wherein said woodparticles and said heavy particles are bonded together by curing saidbonding agent at a temperature in the range from about 400 to 1,000p.s.i. for a time period of about 5 to 30 minutes.
 9. Panel as definedby claim 5 wherein the amount of heavy particles used in the core isabout 75 to 125 percent by weight based on the wood core particles andthe amount of heavy particles used in the face plies is about 25 to 50percent by weight based on the weight of the wood face ply particles.